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THE AGRICULTURAL NEWS. 



De embeb 18, 1915. 



PLANT DISEASES. 



REVIEW OF INFORMATION CONCERN- 

 ING PLANT DISEASES AND RELATED 

 SUBJECTS. 



In accordance with pasl custom there is given below 

 a classified resume oi the articles and reviews which have 

 appeared in this Journal under the headings Fungus Notes 

 and Plant Diseases during the year L915. 



i 111: I S TREES. 



The outbreak of a citrus disease of unexampled severity 

 in Florida and some other sections of the United States has 

 been the subject oi several notes as information has from 

 time to time come through It is believed to have been 

 introduced on stocks imported from Japan. It affects 

 principally the leaves and twigs, and has received the name 

 of Citrus Canker. It is specially severe on grapefruit, but 

 attack-, other citrus species and varieties to some extent. 

 Exactly how serious it promises, to be in its effects on 

 oranges and limes does not appear in the information .so tar 

 received. The first announcement as to the causative 

 organism came from the Florida Experiment Station and was 

 to the effect that the disease is due to a fungus of the genus 

 Phyllosticta. Later work in the laboratory of the Bureau 

 of Plant Industry produced convincing evidence that a 

 bacterium, Pseudomonas citri, is the actual parasite. Special 

 precautions against the introduction of this disease have 

 been taken by the governments of the various West Indian 

 Islands in which citrus industries exist, and the importance 

 of the case calls for tlie willing co-operation of the general 

 public with the officers charged with the duties of inspection 

 if imported plants. 



The notes referring to this subject appeared on pages 1 4, 

 16, 62, ami 206. 



Two reports dealing with the investigation of citrus 

 diseases have been reviewed, one from Florida (p. 94), and the 

 other from the Isle of Pines (p. 318). The former includes 

 notes on the effect of Bordeaux mixture on die-back (of the 

 type supposed to be due to physiological causes), on the 

 artificial production of gummosis by means of various 

 chemicals, and on the successful use of fungicides in 

 preventing melanose. 



The principal matters of interest in the Isle of Pines 

 report concern wither-tip and die back troubles. The former 

 i- attributed to a fungus which does not appear to be present 

 in the Lesser Antilles, and is said to cause serious damage to 

 the 'native lime'. The die-back is believed to be due to 

 a species of Diplodia which is regarded as the most serious 

 citrus enemy in the island. Besides die-back- of large 

 branches, it causes tin- only destructive rot of the mature 

 fruit. This tends to confirm observations made by the 

 present writer in Montserrat, a note as to which is given on 

 the same page as the review. On page 334 the important 

 question of the effects oi exposure on lime trees is discussed, 

 views on tlie subject being contributed by the principal 

 Lgricultural officers oi Dominica and St. Lucia. Instructed 

 pinion is unanimous that efficient shelter is of tin greatest 



importance in lime cultivation. Pamphlet No. 79 of the 



Imperial Department of Agriculture, dealing \\ith the 



disease.-, of linn- trees in forest districts in the West Indies 



(black io.,t disease, red rool disease, and pink disease) is re- 

 viewed on page 302. 



The internal disease of cotton bolls is discussed in two 



articles on pages 222. and 238. This is an affection which 

 has received most attention in Montserrat, bill which occurs 

 in Antigua, St. Vincent, ilc \ irgin Islands, and probably in 

 the other cottoi islands with the exception of 



Barbados. Bolls with, an unblemished exterior are found 

 while still unripe to contain rotted lint and swollen 

 germinating seeds. A specific fungus is usually present, but 

 its place in some instances is taken by a rod-shaped 

 bacterium. Investigations in Montserrat, though not yet 

 fully reported on, leave little room for doubt that the first 

 cause of the injury is the puncturing of the wall of the boll 

 by cotton stainer bugs. The method of infection which 

 leads to the subsequent rot is not known. 



MISCELLANE01 s CROPS. 



An outline is given' on page 30 of the information on 

 diseases contained in two recent monographs on tropical 

 cultivated plants: Professor Copeland's book on the coco-nut 

 and I lr. van Hall's on cacao. 



On page t<> appears a summary of a Michigan bulletin 

 on two diseases of beans ^Phaseolus spp.)i anthracnose and 

 bacterial blight. A disease of the latter type is common in 

 the West Indies. No fully effective means of control is 

 known. 



The increased attention now being given to Indian corn in 

 certain West Indian Islands prompted an article on the rust 

 and smut diseases affecting the maize plant (p. 78). The 

 occurrence of Brown JPnst due to Puccinia maydu, Per., in 

 Montserrat is dealt with; it is not known to have been 

 previously recorded from these islands. The corn smut due 

 to Ustilago Zeae, Ung., is widely distributed in the 

 West Indies, but appears never to assume epidemic form. 

 Puccinia purpurea Cke ., is very common on sorghum, but 

 does not appear to have been recorded locally as occurring on 

 maize. 



A preliminary note on a disease of the papaw tree, 

 which does not seem to have been previously described, 

 appears on page 174. It has been found occasionally in 

 Barbados, and specimens have been received from Montserrat. 

 It occurs on leaves and fruits, but is most serious in its 

 effects on the stem, where it produces a localised rot which 

 results in the death of the tree. It is apparently due to 

 a species of Colletotrichuni. 



On the same page as the above is a note on cassava 

 diseases in the West Indies, and a brief review of articles 

 which deal with two root diseases of llevea in Malaya. 



A very serious bacterial disease of mangoes which has 

 arisen and assumed epidemic form in South Africa is the 

 subject of a note on page 302. It attacks the fruit and has 

 proved capable of destroying the whole crop of an orchard. 

 No remedial measures as yet tried have proved effective in 

 controlling the disease. 



A review of a report on a visit to .lava i page 287)contains 

 a reference to an exceedingly interesting piece of evidence 

 regarding specific resistance to plant disease. Arabian coffee 

 has been replaced in -lava and elsewhere by the l.iberian 

 species, owing to the immunity of the latter to the notorious 

 coffee rust. Bui althoughHhis quality was quite definite for 



some years, and is still retained against the rust as it exists 



in other countries, the fungus in Java appears to have adapted 

 itseli t" the newer host, and n >\\ affects it with approximately 

 equal virulence. No other interpretation of the facts seems 

 to be possible. It is a now familiar fact that in tin 1 case ..| 

 certain rusts the fungus which attacks a species A of the host. 

 gen •' i innot be directly transferred to another species C, 



